Generally, the Internet Protocol (IP) protocol and IP networks have been designed to support a single, best-effort class of service. IP networks have successfully transported TCP-mediated data traffic. As a result, there is a convergence effort to migrate all networked applications, such as voice and videoconferencing applications, to use IP networks as the common transport medium. Best-effort service, however, is not sufficient to meet the Quality-of-Service (QoS) needs of these next-generation applications, especially in an enterprise environment.
A challenging problem for IP networks is efficient admission control (AC). Admission control is required, for example, to support QoS for many inelastic applications. A number of techniques have been proposed or suggested for admission control in packet-switched networks. For example, resource-based admission control (RBAC) methods reserve sufficient network resources for an application on a per-flow basis to handle specified peak bandwidth needs. While generally providing guaranteed QoS, RBAC techniques ignore statistical multiplexing and are therefore inefficient in the sense that additional flows could typically be admitted without experiencing QoS degradation.
More recently, measurement-based admission control (MBAC) methods have been proposed that learn the statistics of network traffic by making on-line measurements. In addition to improving the number of calls supported within a given bandwidth, when compared to RBAC methods, MBAC methods require simpler traffic specifications and are simpler to analyze and design. MBAC methods may be categorized as passive, active, or hybrid techniques. Passive MBAC techniques measure statistics of actual bearer (non-synthetic) traffic. Active MBAC techniques probe the network with synthetic traffic. Hybrid methods combine passive and active methods to improve accuracy and reduce active traffic loads.
While existing MBAC techniques exhibit improved efficiency, by admitting a greater number of calls before unnecessary blocking is experienced, they suffer from a number of limitations, which if overcome, could further improve the utility and efficiency of admission control techniques in packet networks, such as IP networks. For example, such MBAC techniques are based on bandwidth measurements. In addition, they often require unavailable or expensive router functionality and do not address end-to-end considerations, focusing on enforcing admission control on a single link instead of on paths between endpoints.
A need therefore exists for methods and apparatus for admission control that determine whether sufficient bandwidth exists, in a statistical sense, across a path to admit the next flow without exceeding a statistically computed bandwidth limit. A further need exists for methods and apparatus for admission control that can map bandwidth loads to QoS values. Existing methods for mapping bandwidth measures to QoS, as described, for example, in L. Yao, “Queuing Analysis and Control of Long Range Dependent Traffic: Applications to Internet Traffic Engineering,” Ph.D. Dissertation, George Washington University, apply only to highly aggregated traffic over high-speed links, and are therefore not appropriate for typical admission control scenarios or customer environments.